Patent application title: METHOD FOR REALIZING TIME SLOT PARTITION AND SPENDING PROCESS OF AN OPTICAL PAYLOAD UNIT IN AN OPTICAL TRANSMISSION NETWORK

Abstract:

A method of time slot partitioning and overhead processing of an optical
channel payload unit in OTN comprises: A. determining the number of time
slots to be partitioned and mapping modes for the OPU based on properties
of service signals; B. assigning reserved values of payload structure
identification bytes in OPU overhead based on the partitioning of the
time slots; and C. assigning values for reserved bits 1 to 6 of
adjustment control bytes to represent a multiframe in the optical channel
payload unit overhead. The present invention partitions the payload area
of the OPU only by redefining overhead bytes in the original
specification and increasing relevant portion of time slot partitioning
in order to increase effectiveness of bandwidth at lower expense and
flexibility of the mapping modes such that the existing network has good
compatibility without being changed greatly.

Claims:

1. A method of time slot partitioning and overhead processing of an
optical channel payload unit in an optical transport network comprising
the following steps:A. determining the number of time slots to be
partitioned for the optical channel payload unit in a payload area based
on properties of service signals, partitioning the time slots in the
payload area and determining mapping modes for services corresponding to
each time slot;B. expending values of payload structure identification
bytes in optical channel payload unit overhead based on the partitioning
of the time slots and storing a mapping structure, the number of the time
slots, and a branch port number and a mapping mode corresponding to each
time slot in the payload structure identification bytes; andC. assigning
values for undefined bits 1 to 6 of adjustment control bytes to represent
a multiframe in the optical channel payload unit overhead, and allocating
an overhead cycle of the optical channel payload unit overhead to each
time slot.

2. The method according to claim 1, wherein when the time slots are
partitioned in the step A, the payload area in an optical transport
network frame is partitioned into n time slots based on the properties of
the service signals, and remaining columns of remainders are filled
fixedly if the total number of columns of the payload area is indivisible
by the number n of the time slots.

3. The method according to claim 1, wherein the mapping modes, in which
services are mapped to the partitioned time slots, in the step A
comprises:packaging first the service signals in a self-defined optical
channel data unit (ODU) format and then mapping asynchronous signals
based on a mapping mode specified in standard G709; ormapping directly
and asynchronously a constant bit rate (CBR) signal of the services into
defined time slots; orpackaging and mapping the service signals into the
time slots using a generic framing procedure (GFP); ormapping the service
signals into the defined time slots using a self-defined mapping mode;
ora combination of the above four mapping modes.

4. The method according to claim 1, wherein the step B further divides
into the following steps:based on association between a multiframe
alignment signal (MFAS) of optical channel transport unit overhead and a
payload structure identification (PSI) of the optical channel payload
unit overhead, redefining the PSI as follows:using an undefined value to
define PSI[0] to represent a time slot partitioning mapping structure of
a corresponding optical channel payload unit;defining other PSI values as
the number of the partitioned time slots, port numbers corresponding to
the time slots and the mapping modes adopt by corresponding time slots.

5. The method according to claim 1, wherein the step C further divides
into the following steps:assigning values for the undefined bits 1 to 6
of the adjustment control bytes (JC) to represent the multiframe in the
optical channel payload unit overhead, a value of the multiframe
indicating that except the PSI in the optical channel payload unit
overhead other overhead cycles are allocated to the n time slots, every n
frames in each time slot being allocated to corresponding optical channel
payload unit (OPU) overhead.

6. The method according to claim 1, wherein the step A further
comprises:implementing concatenated use for defined time slots through a
virtual concatenation method standardized in the standard G709 after the
time slot partitioning of the optical channel payload unit in the payload
area are performed.

7. The method according to claim 1, further comprising when concatenated
use for defined time slots is implemented, implementing binding of the
time slots by defining sequence numbers (SQ) in the overhead to support
the concatenated use of the time slots.

8. The method according to claim 4, wherein the association between the
multiframe alignment signal (MFAS) of the optical channel transport unit
(OTU) overhead and the payload structure identification (PSI) of the
optical channel payload unit overhead is as follows:when the MFAS is 0,
corresponding PSI byte represents payload type; andwhen the MFAS is
another value, a value corresponding to PSI[0] is associated:using an
undefined value to define PSI[0] to represent a time slot partitioning
mapping structure of corresponding optical channel payload unit;defining
other PSI values as the number of the partitioned time slots, the port
numbers corresponding to the time slots and the mapping modes used by
corresponding time slots.

9. The method according to claim 8, wherein when the MFAS is another value
except 0, the value corresponding to PSI[0] is associated:when PSI[0] is
0X21, a multiplexing structure of the OPU is represented, the number of
the partitioned time slots is assigned to PSI[1], PSI[2]˜PSI[n+1]
are defined as the branch port numbers, and PSI[n+2]˜PSI[2n+1] are
defined as mapping modes adopted corresponding to the partitioned time
slots.

10. The method according to claim 1, wherein the number of the time slots
is determined based on bandwidth of service signals and/or properties of
transmission requirements.

11. The method according to claim 2, wherein the number of the time slots
is determined based on bandwidth of service signals and/or properties of
transmission requirements.

Description:

TECHNICAL FIELD

[0001]The present invention relates to optical transport network, and more
particularly, to a method of time slot partitioning and overhead
processing of an optical channel payload unit in an optical transport
network.

TECHNICAL BACKGROUND

[0002]Optical transport hierarchy (OTH) has many advantages, such as
greater switch granularity, transparent transmission for services, higher
packaging efficiency, etc., as compared to traditional synchronous
transport hierarchy (SDH). In particular, with the decrease of proportion
of voice services and the increase of proportion of data services via
Ethernet and optical fiber channel etc., in recent years, the traditional
transport hierarchy of SDH has been no longer suitable for transmission
of such services. The OTH replaces gradually the SDH in the fields of
metro and backbone transport and becomes a new transport standard.

[0003]An optical transport network (OTN) defined by the OTH adopts various
packaging levels, such as an optical channel payload unit (OPU), an
optical channel data unit (ODU) and an optical channel transport unit
(OTU), to package constant bit rates (CBR) of 2.5G, 10G, 40 Gbit/s into 3
different OTN line rates respectively for transparent transmission using
the same frame structure so as to solve nontransparency in the SDH such
that client services can be better maintained and managed in an
environment where a number of operators coexist. The optical channel
payload unit (OPU) includes an OPU overhead area and payload area, as
shown in FIG. 2.

[0004]However, since data services in the initial stage of formulating the
OTH are not as developed as today, the definition of data packaging
format primarily considers how to solve the transparent transmission of
CBR services, such as the SDH. Therefore, although the OTN may have good
adaptability to services, such as the SDH, it is short of consideration
for today's more data services, resulting in a series of questions, such
as lower packaging efficiency, fewer mapping modes, too simple overhead
definition, etc.

[0005]For example, there is no better solution for plenty of Ethernet GE
signals on the network. Since the minimum particle packaged by the OTN is
2.5G, if only one GE signal is packaged, the packaging efficiency will be
very low. There are different bit rates, such as 2G, 4G, 8G, 10 Gbit/s,
within a range from 2.5G to 10G in the optical fiber channel (FC), but
the OTN has no corresponding packaging format. Thus, if the packaged
particle of ODU1 is used, then a virtual concatenation method, which is
very complicated to implement and in which the packaging efficiency is
not always satisfactory, is required to be adopted.

[0006]The G. 709 specification established by the ITU-T standards
organization defines and standardizes characteristics of the OTN.

[0007]As shown in FIG. 1, a frame structure of the OTN is composed of 4
rows and 4080 columns, i.e., a total of 4×4080=16320 bytes, where
columns 1 to 16 form an overhead area, columns 17 to 3824 form a payload
area, and columns 3825 to 4080 form a forward error correction (FEC)
area.

[0008]The overhead area in the frame structure is further divided as
follows: bytes 1 to 6 in row 1 form a frame indication area, byte 7 is a
multiFrame alignment signal (MFAS), where 256 multiframes are allowed.
Columns 8 to 14 in row 1 form an OTU overhead area, columns 1 to 14 in
rows 2 to 4 form an ODU overhead area, and columns 15 and 16 in rows 1 to
4 form an OPU overhead area.

[0010]The three OTU bit rates illustrated in Table 1 correspond to their
respective ODU and OPU bit rates, reference to the ITU-T standard G.709
may be made with respect to their detailed characteristics.

[0011]The same frame structure and different frame frequencies are used by
the OTN system at different line rates.

[0012]In the field, there have been several similar partitioning methods
of time slot partitioning of the OPU in payload area in order to transfer
client services efficiently and simply. However, these methods all have
some defects and can not better adapt to different situations, or their
using space can not be expanded greatly in the future. Their
disadvantages will be described below:

[0013]1. the method of time slot partitioning is too simple and is
inferred only from an ODU multiplexing structure, and various mapping
situations are not considered strictly;

[0014]2. the definition of overhead is very complicated and difficult to
manage, the method of bandwidth partitioning and time slot multiplexing
is ill-considered and its application range is limited;

[0015]3. a private packaging format is required to be self-defined to
package different client signals; and

[0016]4. various mapping modes and types of client service signals which
may appear in future development are ill-considered, leaving no
sufficient space, etc.

SUMMARY OF THE INVENTION

[0017]A technical problem to be solved by the present invention is to
provide a method of time slot partitioning and overhead processing of an
optical channel payload unit in an optical transport network in order to
avoid disadvantages of complicated overhead definition, weak adaptive
ability and insufficient extension ability in the existing partitioning
scheme to adapt to various different client signals and improve
effectiveness of transport layer bandwidth.

[0018]In order to solve the technical problem described above, the present
invention provides a method of time slot partitioning and overhead
processing of an optical channel payload unit in an optical transport
network comprising the following steps:

[0019]A. determining the number of time slots to be partitioned for the
optical channel payload unit in a payload area based on properties of
service signals, partitioning the time slots in the payload area and
determining mapping modes for services corresponding to each time slot;

[0020]B. expending values of payload structure identification bytes in
optical channel payload unit overhead based on the partitioning of the
time slots and storing a mapping structure, the number of the time slots,
and a branch port number and a mapping mode corresponding to each time
slot in the payload structure identification bytes; and

[0021]C. assigning values for undefined bits 1 to 6 of adjustment control
bytes to represent a multiframe in the optical channel payload unit
overhead, and allocating an overhead cycle of the optical channel payload
unit overhead to each time slot.

[0022]Further, the method may have the following characteristics: when the
time slots are partitioned in the step A, the payload area in an optical
transport network frame is partitioned into n time slots based on the
properties of the service signals, and remaining columns of remainders
are filled fixedly if the total number of columns of the payload area is
indivisible by the number n of the time slots.

[0023]Further, the method may have the following characteristics: the
mapping modes, in which services are mapped to the partitioned time
slots, in the step A comprises:

[0024]packaging first the service signals in a self-defined optical
channel data unit (ODU) format and then mapping asynchronous signals
based on a mapping mode specified in standard G709; or

[0025]mapping directly and asynchronously a constant bit rate (CBR) signal
of the services into the defined time slots; or

[0026]packaging and mapping the service signals into the time slots using
a generic framing procedure (GFP); or

[0027]mapping the service signals into the defined time slots using the
self-defined mapping mode; or

[0028]a combination of the above four mapping modes.

[0029]Further, the method may have the following characteristics: the step
B further divides into the following steps:

[0030]based on association between a multiframe alignment signal (MFAS) of
optical channel transport unit overhead and a payload structure
identification (PSI) of the optical channel payload unit overhead,
redefining the PSI as follows:

[0031]PSI[0] is defined as a value representing a time slot partitioning
mapping structure of a corresponding optical channel payload unit;

[0032]the number of the partitioned time slots is assigned as an
originally preserved PSI[1];

[0033]PSI[2]˜PSI[n+1] are defined as the branch port numbers
corresponding to the partitioned time slots; and

[0034]PSI[n+2]˜PSI[2n+1] are defined as mapping modes adopted
corresponding to the partitioned time slots.

[0035]Further, the method may have the following characteristics: the step
C further divides into the following steps:

[0036]assigning values for the undefined bits 1 to 6 of the adjustment
control bytes (JC) to represent the multiframe in the optical channel
payload unit overhead, a value of the multiframe indicating that except
the PSI in the optical channel payload unit overhead other overhead
cycles are allocated to the n time slots, every n frames in each time
slot being allocated to the corresponding optical channel payload unit
(OPU) overhead.

[0037]Further, the method may have the following characteristics: the step
A further comprises:

[0038]implementing concatenated use for the defined time slots through a
virtual concatenation method standardized in the standard G709 after the
time slot partitioning of the optical channel payload unit in the payload
area are performed.

[0039]Further, the method may have the following characteristics: when
concatenated use for the defined time slots is implemented, implementing
binding of the time slots by defining sequence numbers (SQ) in the
overhead to support the concatenated use of the time slots.

[0040]Further, the method may have following characteristics: the
association between the multiframe alignment signal (MFAS) of the optical
channel transport unit (OTU) overhead and the payload structure
identification (PSI) of the optical channel payload unit overhead is as
follows:

[0042]when the MFAS is another value, a value corresponding to PSI[0] is
associated:

[0043]when PSI[0] is 0X20, a multiplexing structure of the ODU is
represented, a value corresponding to PSI[1] is a reserved value, and
PSI[2] PSI[17] represent a port corresponding to each branch and the type
of the ODU for the branch; and

[0044]when PSI[0] is 0X21, a multiplexing structure of the OPU is
represented, the number of the partitioned time slots is assigned to
PSI[1], PSI[2]˜PSI[n+1] are defined as the branch port numbers, and
PSI[n+2]˜PSI[2n+1] are defined as mapping modes adopted
corresponding to the partitioned time slots.

[0045]Further, the method may have the following characteristics: the
number of the time slots is determined based on bandwidth of service
signals and/or properties of transmission requirements.

[0046]The present invention may partition the payload area of the OPU only
by redefining overhead bytes in the original specification and increasing
relevant portion of time slot partitioning in order to increase
effectiveness of bandwidth at lower expense and flexibility of the
mapping modes such that the existing network has good compatibility
without being changed greatly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 illustrates a schematic diagram of a frame construct of an
optical transport network (OTN) in prior art;

[0048]FIG. 2 illustrates time slot partitioning and mapping of the OTN in
accordance with the present invention;

[0049]FIG. 3 illustrates values of PSI when an ODU defined in the G709 is
a multiplexing structure;

[0050]FIG. 4 illustrates the definition of the OPU overhead bytes PSI and
JC; and

[0051]FIG. 5 illustrates the definition of the OPU overhead in a
concatenation manner specified in the ITU-T specification.

PREFERRED EMBODIMENTS OF THE INVENTION

[0052]The technical scheme of the present invention will be described in
detail below in conjunction with the accompanying drawings and specific
embodiments.

[0053]The present invention provides a method of time slot partitioning
and overhead processing of an optical channel payload unit in an optical
transport network comprising determining the number of time slots to be
partitioned for the optical channel payload unit in a payload area based
on properties of service signals (bandwidth of the service signals and/or
properties of transmission requirements), partitioning the time slots in
the payload area and determining mapping modes for services corresponding
to each time slot; expending values of payload structure identification
bytes in optical channel payload unit overhead based on the partitioning
of the time slots, and storing a mapping structure, the number of the
time slots, and branch port numbers and a mapping mode corresponding to
each time slot in the payload structure identification bytes; and
assigning values for undefined bits 1 to 6 of adjustment control bytes to
represent a multiframe in the optical channel payload unit overhead, and
allocating an overhead cycle of the optical channel payload unit overhead
to each time slot.

[0054]When the time slots are partitioned in the optical channel payload
unit (OPU) in the optical transport network (OTN), multiFrame alignment
signal (MFAS) of an OTN frame structure are associated with PSI bytes of
the OPU overhead such that the PSI bytes corresponding to different
values of the MFAS have different definitions, where an existing PSI
value is redefined, while a definition of the PSI value is extended so as
to add a new PSI value to adapt to the time slot partitioning of the OPU
in the payload area without affecting the original equipment functions.

[0055]A definition of adjustment control (JC) bytes in row 1 and column 16
in an OPU overhead area is added, and values of 6 original reserved bits
are defined as new multiframe values of the partitioned time slots such
that the number of the partitioned time slots is not limited by the
original multiframe alignment signal (MFAS). That is, the original
multiframe value of the MFAS remains unchanged and the new multiframe
values indicate the OPU overhead to be allocated to different time slots
such that each time slot can use the OPU overhead cyclically.

[0056]If it is required to combine and use some partitioned time slots to
achieve large bandwidth, overhead in rows 1, 2 and 3 and column 15 of an
OTN frame may be used and reference to the definition of virtual
concatenation specified in the G709 which is proposed by the ITU-T is
made so as to use simply these overhead bytes and implement the
concatenated use of the time slots, as shown in FIG. 4.

[0057]In the present invention, time slot partitioning is implemented
flexibly for the OPU structure of the OTN frame, overhead resources are
allocated reasonably, various mapping modes are adapted to, the
effectiveness of bandwidth is improved, and the problems that the mapping
modes are too simple and the number of the mapped branches are not the
power of 2 for different service bit rates in future in the ITU-T
standard specification G709 are well solved. The present invention's
emphasis lies in adding and modifying contents of the OPU overhead bytes,
and defining and managing time slot partitioning of the OPU in a device
using some undefined overhead.

[0058]For the method in accordance with the present invention, its
specific implementation is based on time slot partitioning of the OPU and
redefinition of the OPU overhead.

[0059]1. the time slot partitioning of the OPU used for implementing the
time slot partitioning for the payload area of the OPU.

[0060]As shown in FIG. 2, flexible time slot partitioning may be
implemented by definition of the overhead in a common OPU structure.

[0061]Assuming a certain OPU is partitioned into n time slots which are
transmitted in byte intercalating and multiplexing manner, if the column
number of the payload area of 3808 is indivisible by n, then the
remaining columns of remainders are filled fixedly. Except the PSI bytes
in the OPU overhead, seven other overhead bytes are allocated cyclically
to n time slots by taking n as a unit. The time slots corresponding to
the overhead are defined by bits 1 to 6 of the overhead byte in row 1 and
column 16, and pointer adjustment and indication are still performed for
bits 7 and 8 according to specification requirements when asynchronous
mapping of CBR signals is performed.

[0062]The time slot partitioning function may support a variety of
flexible mapping modes for client signals. As shown in FIG. 2, the client
signals may be mapped into the defined time slots using various mapping
modes. For example, the client signals are first packaged in a
self-defined ODU format, and then the mapping of asynchronous signals is
performed according to the mapping modes described in a standard, such as
the standard G709, or constant bit rate (CBR) signals of the client are
mapped directly and asynchronously into the defined time slots, or the
client signals are packaged and mapped into the time slots using a
generic framing procedure (GFP), or the client signals may be mapped into
the defined time slots by the self-defined mapping modes. The present
invention supports a variety of mapping modes for various client signals
through the definition of the associated overhead bytes of the OPU and is
not limited to the mapping modes specified in the standard.

[0063]The time slot partitioning function may also support the
concatenated use function of the time slots. According to the present
invention, after the time slot partitioning of the OPU in the payload
area is performed, a virtual concatenation method standardized by a
standard, such as the standard G709, may be adopted to achieve the
concatenated use of the defined time slots. However, the concatenated use
can be simplified. For example, when the defined time slots are
transmitted via the same path, the effect of propagation delay may not be
considered and the multiframe alignment signal of concatenation does not
need to be defined. When dynamic increasing or decreasing of link
capacity is not required to be considered, information, such as link
state, is not needed to be processed. In fact, the simplified use is that
the binding of the time slots may be achieved only by defining the
sequence number (SQ) in the overhead.

[0064]2. the definition of the OPU overhead bytes used for extending the
definition of the bytes in the OPU overhead area.

[0065](1) As shown in FIG. 1, in the frame structure defined in the
standard G709, the definition of the PSI bytes of the OPU overhead is
associated with the multiframe alignment signal (MFAS) of the OTU
overhead. When the MFAS is 0, the corresponding PSI byte represents the
payload type, as shown in Table 2.

[0066]When the MFAS is another value, it is associated with a value
corresponding to PSI[0]. For example, when PSI[0] is 0X20, it represents
the ODU multiplexing structure, the value corresponding to PSI[1] is a
reserved value, and PSI[2] PSI[17] represent a port corresponding to each
branch and the type of the ODU for the branch, as shown in FIG. 3.

[0067]The present invention uses an undefined value to define PSI[0] to
represent a time slot partitioning mapping structure of the corresponding
optical channel payload unit, and defines other PSI values as the number
of the partitioned time slots, the port numbers corresponding to the time
slots and the mapping modes used by the corresponding time slots.

[0068]In the present invention, the time slot partitioning is also a
multiplexing structure which is different from the multiplexing structure
of the ODU. Thus, a new value, such as 0X21, is needed to be defined in
PSI[0].

[0069]The originally preserved PSI[1] is assigned as the number of the
partitioned time slots, as shown in FIG. 4.

[0070]PSI[2]˜PSI[n+1] are defined as the branch port numbers and
PSI[n+2]˜PSI[2n+1] are defined as the used mapping modes.

[0071](2) Considering the number of the partitioned time slots may not be
the power of 2, thus, it can not be cycled in 256 multiframe periods and
a new multiframe alignment signal is required to be defined.

[0072]Bits 1 to 6 in the first overhead byte in column 16 are used to
define the multiframe alignment signal. This multiframe is cycled from 0
to n-1 corresponding to 1 to n time slots, respectively, by the number of
the time slots. The OPU overhead corresponding to the value of the
multiframe is allocated to the corresponding time slot number, thus,
every n frames in each time slot may be allocated to the corresponding
OPU overhead.

[0073](3) For some applications where bandwidth is extended by binding a
time slot, reference to the definition of virtual concatenation in the
standard G709 is made, as shown in FIG. 5. In virtual concatenation
overhead (VCOH), the value of SQ is defined such that a receiver can know
the order corresponding to the time slot in the binding application.

[0074]An implementation scheme will be described in detail by one
particular application example in accordance with the present invention.
The implementation scheme comprises the following steps:

[0075]step 110: based on properties such as bandwidth of client signals
and transmission requirements, to determine the number of time slots to
be partitioned for the optical channel payload unit in a payload area,
the mapping modes used by time slots for the client signals to the OPU,
and whether it is required to bind and use some time slots, and to fill
the remaining columns in the OPU area with fixed signals;

[0076]step 120: to associate a MFAS value in the OTU overhead with a PSI
value in the OPU overhead, and to assign different values to the PSI for
different MFAS values such that PSI[0] to PSI[2n+1] have different
meanings, noting that the definition of these values is significant only
when the time slot partitioning for the OPU is required and the
definition of the PSI value complies with the requirements of the
standard G709 when the time slot partitioning is not supported;

[0077]step 130: to define a value in row 1 and column 16 in the OPU
overhead, and to assign values to the original undefined bits 1 to 6 to
represent a multiframe alignment signal which indicates allocating
overhead cycles of the OPU to each time slots using the number of the
partitioned time slots of the OPU as a period, where this multiframe
alignment signal is different from that in the OTU overhead; and

[0078]step 140: other overhead values of OPU will have different
definitions according to different mapping modes, for example, for
applications where the binding of time slots is required, the definition
of overhead in rows 1 to 3 and column 15 is the same as the definition
when there is virtual concatenation, and whether pointer adjustment is
performed for the overheads in rows 1 to 4 and column 16 is determined
based on whether asynchronous mapping is required to be performed. When
the mapping mode is GFP mapping, all of the overheads have no
significance.

[0079]In the present invention, the number of the time slots and the
concatenation method are configured flexibly based on bandwidth of the
client signals and the mapping modes according to the technical scheme of
time slot partitioning of the OPU in the payload area. For example, when
GE client signals are transmitted in the structure of OPU1, the OPU1 area
may be selected to be partitioned into 2 time slots with bytes
intercalated so as to perform the mapping of 2-channel GE signals from GE
to the time slots. Both information after 64/65B coding and media access
control (MAC) signals before 8B/10B coding may be transmitted according
to the GFP-T specification requirements. When bandwidth of the time slots
is sufficient, mapping directly and asynchronously signals at physical
layer of the Ethernet may implement transmission of Ethernet clock,
thereby achieving requirements of synchronous Ethernet specifications.
When FC client signals, such as 2G, 4G and 8G, are transmitted in OPU2,
time slot partitioning for 10G bandwidth may be implemented in term of
the transmitted minimum granularity, 2G. Thus, several different FC
signals described above may be transmitted mixedly to facilitate
management and improve bandwidth utilization ratio.

[0080]In conclusion, the method in accordance with the present invention
has following characteristics:

[0081](1) different quantities of time slots may be allocated flexibly in
the fixed OPU structure;

[0082](2) client services may be mapped into one or more time slots using
different mapping modes;

[0083](3) each time slot may obtain periodically services for the OPU
overhead, where a cycle period is the number of the partitioned time
slots;

[0085](5) the same type of client signals may adopt different mapping
modes to obtain different services, for example, Ethernet signals may be
mapped asynchronously into the time slots to obtain clock information at
a receiver in order to solve the problem of synchronizing clock
transmission of the Ethernet;

[0086](6) the PSI bytes are redefined, the number of ports that the OPU
can support is extended, for example, although only 16 port numbers are
defined originally in the G709 specifications, the OPU can support 256
port numbers after the definition is extended;

[0087](7) the same time slot partitioning scheme may be equally
implemented in OPU1/OPU2/OPU3, even OPU4 to be defined in the future; and

[0088](8) the defined time slot partitioning method may be compatible with
the original device when signals are not needed to be input/output at an
intermediate node during a transmission process, that is, the newly added
functions may be transmitted transparently in the original network. The
intermediate node may not necessarily concern particular mapping modes,
and only service end point needs the corresponding ability of receiving
signals.

[0089]Of course, many other embodiments in accordance with the present
invention may be used. Various corresponding modifications and variations
may be made by those skilled in the art according to the present
invention without departing from the spirit and essence of the present
invention. However, all of these corresponding modifications and
variations should fall within the protection scope defined by the
appended claim.

INDUSTRIAL APPLICABILITY

[0090]The present invention may partition the payload area of the OPU only
by redefining overhead bytes in the original specification and increasing
relevant portion of time slot partitioning in order to increase
effectiveness of bandwidth at lower expense and flexibility of the
mapping modes such that the existing network has good compatibility
without being changed greatly.